COLLAPSIBLE STEERING COLUMN ASSEMBLY

Abstract: A collapsible steering column assembly with means to absorb energy transmitted by the steering column upon collapse, including a deformable U-shaped wire clip (7) engaged around a pair of pins (10). A skid member (9) adjoins the clip (7) and is coupled to the steering column so that, upon collapse of the steering column, the skid member is urged in a direction to deform the wire clip by drawing it over the pins (10). The clip and skid member are accommodated in a fixed mounting bracket (8) for the steering column. In an alternative embodiment (Figs. 5, 6), the pins (10A) are secured to a mouveable plate (12) so that the plate moves upon vehicle impact to straighten the two wires (7A) around the pins, one end (15) of each wire being secured in a fixed plate (14).

Description: COLLAPSIBLE STEERING COLUMN ASSEMBLY This invention relates to a collapsible steering column assembly. GB 1 120 799 discloses a collapsible steering column which is connected to a deformable element in the form of a flexible metal rod which is spot welded to the column and which is passed around a pair of rollers so that collapse of the steering column pulls the rod around the rollers and in so doing deforms the rod and thus retards the collapse of the steering column. According to the present invention, there is provided a collapsible steering column assembly including means to absorb energy transmitted by the steering column upon collapse, said means including a deformable element associated with a mounting means of the steering column, the mounting means including a mounting bracket slidably housing a skid member coupled to the steering column and adjoining said deformable element, so that, upon collapse of the steering column, said skid member is urged in a direction to deform said deformable element which thereby absorbs collapse energy, characterised in that said deformable element is in the form of a length of deformable wire with arms embracing a pin, over which said wire is caused to be drawn by said skid member, thereby to absorb energy. Thus, the means to absorb collapse energy is transferred from the immediate surround of the steering column to the region of the mounting bracket. The deformable wire may be in the form of a clip bent around two spaced pins with the skid member being located between the pins. Accordingly, upon collapse of the steering column, the skid member is urged between the pins and drags with it the wire clip which is pulled over and around the pins. The outer ends of the wire clip can be confined within a chamber of the mounting bracket to prevent splaying thereof. In an alternative form, there may be one or two separate wires, each wire embracing its own pin and being secured at one end. The pin in this case is fixed to the skid member so that movement of the pin causes the wire to be drawn around it. Two spaced apart pins may thus be provided, each with their own length of wire. The or each member fixing one end of the or each wire, respectively, may be itself mounted by means of shear means such as shear pins which are provided to take the initial force of the pull on the or each wire and then subsequently allow the fixing means to break away. As with the first embodiment, the outer end of the or each wire can be confined by a member to prevent splaying of the wire. In each embodiment, the or each wire can be arranged to deform by extension of the wire as it is drawn around its associated pin. In the second embodiment, the wire can be doubled back on itself so as to embrace its associated pin twice. For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:- Figure 1 is a diagrammatic side view of one embodiment of a collapsible steering column assembly / Figure 2 is a diagrammatic view, partly in section, of part of the steering column assembly shown in Figure 1, viewed in the direction of arrow A before steering column collapse, Figure 3 is a view similar to Figure 2, viewed in the direction of arrow A, after steering column collapse, Figure 4 is a sectional view taken along the line IV-IV in Figure 2, Figure 5 is a diagrammatic plan view of a second embodiment of a collapsible steering column assembly, Figure 6 is a diagrammatic plan view of the embodiment shown in Figure 5, Figure 7 is a diagrammatic side view similar to Figure 5 but showing a modification thereof, Figure 8 is a typical view of a deformable wire bent into a primary form prior to mounting in the embodiment shown in Figure 7, and Figure 9 is a graph of load against extension to illustrate energy absorbtion value as the steering column collapses. Referring to Figure 1, the steering column assembly includes a steering rack 1, a lower, fixed mounting point 2, an inner shaft 3 of the steering column, an outer shaft 4 of the steering column, a steering wheel 5 and an upper fixed mounting point 6 for the steering column. In the form illustrated in Figure 1, the steering column is shown as being adjustable but the present invention can equally apply to a rigid steering column assembly. Referring generally to Figures 1 to 4, the means to absorb energy transmitted by the steering column upon collapse, which occurs in the direction of arrow B, includes a deformable element in the form of a wire clip 7 associated with the upper mounting means 6. The mounting means 6 includes a mounting bracket 8 which slidably houses in grooves 8A a skid member 9. The skid member 9 is coupled to the outer shaft 4 and is located adjoining the wire clip 7. As shown in Figure 2, the wire clip before steering column collapse is generally U-shaped with the two arms of the U located about two spaced apart pins 10, the spacing of the pins 10 being such that the skid member 9 can pass between them in the grooves 8A. The outer, free arms of the clip 7 are confined within the bracket as illustrated at 8B, thus serving as a track, in order to prevent splaying of the arms. Upon vehicle crash, the steering wheel 5 is caused to move in the direction of arrow B and the skid member 9 is thereby urged in the same direction to engage and draw with it the clip 7, whose arms are dragged over the pins 10 as illustrated in Figure 3, this having the effect of absorbing the energy transmitted by the steering column upon collapse. Collapse of the steering column itself is accommodated by relative collapse between the inner shaft 3 and outer shaft 4 in the region of reference numeral 11. Figures 5 and 6 show an alternative embodiment in which the wire is, at least initially, held in a single location and movement of a pin, fixed to the skid member, causes deformation of the wire. More specifically, there are two lengths of wire 7A, each drawn around an associated pin 10A. Each pin 10A is fixed to a top plate 12. A plate 13 with a hooked end 14 is secured in a mounting block 15, the plate 13 receiving one end of the wire 7A at 15, the end being secured by means of a rivet or the like. The plate 13 and mounting block 15 are in each case secured by respective bolts (not shown) through bolt holes 16 to the chassis of the vehicle. Each wire 7A is bent around its associated pin 10A and is confined by a metal side plate 17 to prevent splaying of the wire as it is drawn around the pin 10A. There are four moulded plastics shear pins 18 which hold the plate 13 and mounting block 15 together with the top plate 12. During impact of the vehicle, the top plate 12 and pins 10A are driven forwards and downwards away from the driver and this causes the wires 7A to be drawn around the pins 10A and stretched. The loose end or free end of each wire is contained by the track formed by the metal side plate 17. The initial force drawing on the plate 13 is taken by the plastics shear pins 18 and once these shear pins are broken, the hooked plates 13, mounting blocks 15 and the energy absorbing wires 7A separate from the top plate 12. In the modification illustrated by Figures 7 and 8, each wire 7A is doubled back on itself through the hook plate 14 so as to bend twice around its associated pin 10A before being secured in the hooked plate 14.

Claims: CLAIMS ; 1. A collapsible steering column assembly including means to absorb energy transmitted by the steering column upon collapse, said means including a deformable element (7) associated with a mounting means (6) of the steering column, the mounting means including a mounting bracket (8) slidably housing a skid member (9) coupled to the steering column and adjoining said deformable element (7) , so that, upon collapse of the steering column, said skid member is urged in a direction to deform said deformable element which thereby absorbs collapse energy, characterised in that said deformable element is in the form of a length of deformable wire (7) with arms embracing a pin (10) , over which said wire is caused to be drawn by said skid member, thereby to absorb energy. 2. An assembly according to claim 1, wherein the arms of the wire are confined within the mounting bracket to prevent splaying. 3. An assembly according to any one of the preceding claims, wherein said skid member is coupled to an outer shaft (4) of the steering column. 4. A steering column assembly according to any one of the preceding claims, and being a non-adjustable steering column. 5. An assembly according to any one of the preceding claims, wherein there are two said pins (10) and said wire is a generally U-shaped wire clip (7) with arms embracing said pins, which are spaced-apart and between which said skid member (9) can pass to draw the clip over the pins to deform it. 6. An assembly according to any one of claims 1 to 4, wherein said pin (10A) is fixed to said skid member (12) so that movement of the pin causes the wire to be drawn around it. 7. An assembly according to claim 6, wherein there are two wires (7A) , each embracing its own pin (10A) . 8. An assembly according to claim 6 or 7, wherein said wire is doubled over so as to embrace its pin twice. 9. An assembly according to claim 6, 7 or 8, wherein said wire is secured at one end to a fixing means (13) which itself is mounted by means of shear means (18) . 10. An assembly according to any one of the preceding claims, wherein said skid member is mounted by means of shear means (18). 11. An assembly according to any one of the preceding claims, wherein said wire is arranged to deform by extension. 12. A steering column assembly according to any one of the preceding claims except claim 4, and being an adjustable steering column assembly. 13. A collapsible steering column assembly, substantially as hereinbefore described with reference to the accompanying drawings.

Inventors: HANCOCK MICHAEL THOMAS, HANCOCK, MICHAEL, THOMAS
Applicants: TORRINGTON CO, THE TORRINGTON COMPANY LIMITED
Application year: 1994
Main classification: B62D1
IPC codes: B62D1, F16F7